Internal combustion engine



FIG. 1 is a front view of the internal combustion engine showing our new design;

FIG. 2 is a rear view of thereof;

FIG. 3 is a right view of thereof;

FIG. 4 is a left side view of thereof;

FIG. 5 is a top (plan) view of thereof; and,

FIG. 6 is a bottom view of thereof. 

The ornamental design for a internal combustion engine, as shown and described. 